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Don’t use the temporary disk to store data. It is only temporary storage, so you would risk losing data that can’t be recovered. Data loss can occur when the virtual machine moves to a different host. Resizing a virtual machine, updating the host, or a hardware failure on the host are some of the reasons a virtual machine might move.
If you have an application that needs to use the D: drive letter, you can reassign drive letters so that the temporary disk uses something other than D:. For instructions, see Change the drive letter of the Windows temporary disk.